After starting as snow for northeastern Ontario, the precipitation is then expected to transition to rain for most areas south of a line from Montreal River to Kirkland Lake by Saturday afternoon.
"During this transition, there is a risk of freezing rain," says EC.
Areas northwest of the system are expected to see all snow with amounts of 10-15 cm possible through Sunday.
The heaviest snow is expected to fall over the Wawa to Timmins corridor.
Warmer air will accompany the rain, with many places seeing daytime highs rise well above the freezing mark Saturday.
"Much of southern Ontario will see a true January thaw with highs of 5-10°C forecast on Saturday," says Weather Network meteorologist Doug Gillham.
That's great news for those looking for a "Wintermission," but it has water conservation authorities on high alert.
"With the warm temperatures and the forecasted rainfall there is the potential for melting a portion of existing snow pack and ice cover on our creeks which will result in higher flows in all of our streams and creeks, resulting in dangerous flow conditions," said the Central Lake Ontario Conservation in a statement Thursday.
Officials say watercourses will be flowing higher than normal causing local streams and creeks to become dangerous. Melting ice may also result in hazardous conditions.
Residents are being asked to stay away from all watercourses and structures such as bridges, culverts and dams.
"Elevated water levels, fast flowing water and slippery conditions along stream banks continue to make these locations extremely dangerous," said the CLOC.
Ponding and flooding are also a concern with the warming temperatures and incoming rain. Toronto city officials say they have crews out with bobcats and front-end loaders trying to open clogged catch basins.
The recent heavy snow across parts of the province combined with the warm-up and rain expected this weekend is raising concerns about possible roof collapses as well.
Officials say the pressure of the snow can be too much for certain buildings and homes to handle and recommend hiring professionals to safely clear the snow.
HOW LONG WILL THE MILD TEMPS LAST?
"We'll continue to see mild conditions for the region on Sunday and Monday, but we'll then step back into a more typical January pattern for the rest of the week (typical rather than extreme temperatures swings) with the potential for a return to well below seasonal by next weekend and/or beyond," says Gillham.
The normal daytime high for this time of year is around -2°C.